Susceptibility of Pinus oocarpa to Armillaria root disease in Zimbabwe

Abstract

The results of susceptibilities to Armillaria heimii Pegler of 30 eight to ten year old Pinus oocarpa clones, with up to 56 ramets each, in five seed orchards are presented. Deaths among clones ranged from nil to 9.36 percent during the four- year study period. Average annual mortalities in seed orchards were 1.20 percent to 5.23 percent. There were statistically significant differences among the clones within and across seed orchards. Duncan’s multiple range comparisons of proportions of dead trees in each clone indicated that clones of South African origin were generally least susceptible. Clones from Nicaragua were most susceptible. There was a significant negative linear progression of symptoms and positive progression of deaths in clones during the study period.